Ebullition cooling devices are adapted to cool heat generating components by heat transport due to the boiling and condensation of refrigerant, and are used in various electronic devices for cooling heat generating components, such as diodes and transistors, incorporated in the device.
Refrigerants of low boiling point for use in ebullition cooling devices are generally fluorocarbons and like expensive refrigerants. Preferably, therefore, ebullition cooling devices have such a construction that the amount of refrigerant to be enclosed therein can be smaller to the greatest possible extent.
Ebullition cooling devices already known for use with heat generating components include the device disclosed, for example, in JP-A No. 8-204075(1996). The disclosed device comprises a boiling unit in the form of a hollow planar plate having a multiplicity of hollow channels in its interior and a side wall outer surface with a heat generating component attached thereto, and a condensing unit in the form of a heat exchanger having plate fins. The hollow planar plate constituting the boiling unit is connected directly to the heat exchanger constituting the condensing unit so as to hold the hollow channels of the former in communication with a header tank of the latter.
The cooling device described above has the boiling unit provided by a hollow planar plate, so that the amount of refrigerant enclosed need not be very great, whereas the arrangement wherein the hollow planar plate is connected directly to the heat exchanger results in a low degree of freedom in designing the device. Accordingly, the device is not fully useful for electronic devices which are compacted or higher in complexity and can not always be installed within such electronic devices.
When the heat receiving position (e.g., the location where a heat generating component is installed) of an electronic device is a large distance away from the heat dissipating position thereof (e.g., the location where a vent is provided), the ebullition cooling device described must be made usable in the electronic device, for example, by giving an increased size to the hollow planar plate. This entails a corresponding increase in the amount of refrigerant enclosed.
Further with the ebullition cooling device described, the heat generating component is attached to the side wall outer surface of the hollow planar plate which has a relatively small thickness, so that increased contact thermal resistance between the plate and the component due to insufficient rigidity of the side wall is likely to result in lower heat dissipating performance.
The above device further has the problem that the refrigerant vapor flowing upward from the boiling unit toward the condensing unit and the refrigerant condensate flowing down from the condensing unit toward the boiling unit interfere with each other at the connection between the two units, i.e., the problem of so-called flooding. This flooding phenomenon degrades the spontaneous circulation of the refrigerant, reducing the maximum amount of heat transport and entailing lower heat dissipating performance, and therefore needs to be prevent to the greatest possible extent.
An object of the present invention is to provide an ebullition cooling device for a heat generating component which device can be designed with increased freedom so as to be fully useful in compacted or complex electronic devices or the like and is reduced in the amount of refrigerant to be enclosed therein and outstanding in heat dissipating performance.